1. Field of the Invention
The present invention relates to a coil winding structure of a transformer, and more particularly, to a cylindrical coil winding structure of a flyback transformer for applying high-voltage current to a cathode-ray tube.
2. Description of the Prior Art
Generally, a cathode-ray tube includes an electron gun emitting a thermal electron beam and a photosensitive screen producing desired colors and images by the emitted electron beam. The photosensitive screen is coated with a combination of R, G and B type fluorescent materials. Also the cathode-ray tube is provided with a deflection coil, a focusing coil and an accelerating coil, etc., for controlling the emitted electron beam.
Typically, the cathode-ray tube requires a high-voltage of 25,000 V or so for deflecting and focusing the electron beam, and this high voltage current is generated by a flyback transformer and applied to the cathode-ray tube.
FIG. 1 is a perspective view illustrating an exploded state of a conventional flyback transformer, which will be described below.
As illustrated in FIG. 1, the conventional flyback transformer includes a casing 10 having a through-hole 12, a cylindrical secondary coil assembly 30 inside the casing 10, a cylindrical primary coil assembly 20 inserted into the secondary coil assembly 30, a magnetizable core 40 inserted into the primary coil assembly 20, an anode cap 14 attached to the secondary coil assembly 30, a cover 50 for the casing 10, and a condenser 52 inside the cover 50, etc.
The primary and secondary coil assemblies 20, 30 respectively consist of an insulating bobbin 24, 34 and primary and secondary coil windings 22, 32 around the bobbins 24, 34. All turns of the coil windings 22, 32 are insulated from each other.
Voltage applied to the flyback transformer is rectified by the condenser 52, flows to the primary coil assembly 20, and consequently to the primary coil winding 22.
The voltage applied to the primary coil winding 22, that is, a primary voltage, provides a large secondary voltage by mutual induction effect. As is well known, the value of the secondary voltage is determined depending on the ratio of the number of turns of the secondary coil winding 32 to that of the primary winding 22. Thereafter, the induced secondary voltage is applied through the anode cap 14 to the cathode-ray tube and then functions by emitting, accelerating, and focusing the electron beam.
In the above-described conventional flyback transformer, however, achieving uniformity in the characteristics thereof is not easy. Namely, in the coil winding process, the adjacent coil turns are very likely to overlap or separate from each other. Therefore, all of those problems lead to variation or fluctuation in the characteristics of the flyback transformer, consequently resulting in poor high voltage regulation thereof.
Furthermore, the demand for large sized cathode-ray tubes has increased, and therefore various devices for supplying voltage to the cathode-ray tube, especially the flyback transformer which requires a greater number of turns in the coil windings, has lead to a resultant increase in the overall size of the flyback transformer.